Oil well pumping systems are well known in the art. Such systems can be used to mechanically remove oil or other fluid from beneath the earth's surface, particularly when the natural pressure in an oil well has diminished. Generally, an oil well pumping system begins with an above-ground pumping unit, which can commonly be referred to as a “pumpjack,” “nodding donkey,” “horsehead pump,” “beam pump,” “sucker rod pump,” and the like. The pumping unit can create a reciprocating up and down pumping action that moves the oil, or other substance being pumped, out of the ground and into a flow line, from which the oil is then taken to a storage tank or other such structure.
Below the ground, a shaft is lined with piping known as “tubing.” Into the tubing is inserted a string of sucker rods, which ultimately is indirectly coupled at its north end to the above-ground pumping unit. The string of sucker rods is ultimately indirectly coupled at its south end to a subsurface or “down-hole” pump that is located at or near the fluid in the oil well. The subsurface pump can have a number of basic components, including a barrel and a plunger. The plunger can operate within the barrel, and the barrel, in turn, is positioned within the tubing. It is common for the barrel to include a standing valve and the plunger to include a traveling valve. The standing valve can have a ball therein, the purpose of which is to regulate the passage of oil from down-hole into the pump, allowing the pumped matter to be moved northward out of the system and into the flow line, while preventing the pumped matter from dropping back southward into the hole. Oil can be permitted to pass through the standing valve and into the pump by the movement of the ball off its seat, and oil is prevented from dropping back into the hole by the seating of the ball. North of the standing valve, coupled to the sucker rods, can be the traveling valve. The traveling valve can regulate the passage of oil from within the pump northward in the direction of the flow line, while preventing the pumped oil from dropping back southward, in the direction of the standing valve and hole.
Actual movement of the pumped substance through the system will now be discussed. Oil is typically pumped from a hole through a series of downstrokes and upstrokes of the pump, which motion is imparted by the above-ground pumping unit. During the upstroke, formation pressure causes the ball in the standing valve to move upward, allowing the oil to pass through the standing valve and into the barrel of the oil pump. This oil can be held in place between the standing valve and the traveling valve. In the traveling valve, the ball is located in the seated position, held there by the pressure from the oil that has been previously pumped.
On the downstroke, the ball in the traveling valve unseats, permitting the oil that has passed through the standing valve to pass there through. Also during the downstroke, the ball in the standing valve seats, prevents pumped oil from moving back down into the hole. The process repeats itself again and again, with oil essentially being moved in stages from the hole, to above the standing valve and in the oil pump, to above the traveling valve and out of the oil pump. As the oil pump fills, the oil passes through the pump and into the tubing. As the tubing is filled, the oil passes into the flow line, and is then taken to the storage tank or other such structure.
There are a number of problems that are regularly encountered during fluid pumping operations. Fluid that is pumped from the ground is generally impure, and includes solid impurities such as sand, pebbles, limestone, grit, iron sulfide, and other sediment and debris. Certain kinds of pumped fluids, such as heavy crude, tend to contain a relatively large amount of solids.
Solid impurities can be harmful to a fluid pumping apparatus and its components for a number of reasons. For example, sand, pebbles, limestone, grit, iron sulfide, and other sediment and debris can become trapped between pump components, causing damage and excessive wear, reducing effectiveness, and sometimes requiring a halt to pumping operations and replacement of the damaged components. These solid impurities frequently collect and become concentrated between the barrel and plunger. In particular, as the amount of space or clearance between the exterior surface of the plunger and the interior surface of the barrel in typical pump plungers and barrels can be as great as 0.01″, this permits a constant passage of fluid, including solid impurities, between the plunger exterior and the barrel interior. During fluid pumping operations, particularly when the pump plunger reciprocates, the collection of solid impurities causes rapid wear to the pump components. Thus, the solid impurities that are contained within the fluid and that pass through the space between the plunger and the barrel score the plunger and barrel surfaces, thereby reducing the operating life of both. In addition, frictional forces generated by the collections of solid impurities can cause excessive stress to be generated throughout the pump and sucker rod string, which often results in sticking of the pump, automatic shut-down of the pumping unit, or a parted sucker rod string.
One prior art solution has been the use of plunger units having large accumulation areas into which the solid impurities can be collected. The accumulation areas in such plunger units are typically approximately 3-5 feet long and are composed of metal. However, such units must be replaced in their entirety when they sustain wear. In general, repairs to or replacement of pump components that become necessary by virtue of the aforementioned damage caused by solid impurities can be time-consuming and expensive.
The present application addresses these problems encountered in prior art pumping systems and provides other, related advantages.